c b a X a a b b c c X a X e b X e c X e 2.2 c b a X a b b c c X c b a X c X c b a X c c X c b a X b b c c X c b a X a a b b c c X c b a X b c c X true c b a X c X c b a X c c X true 2 1 a 1 0 1 0 0 1 1 1 b 1 0 0 1 1 1 1 0 c 1 0 1 0 1 1 1 18524 c 1 1 0 0 0 1 0 0 e 0 1 0 a 1 0 0 b 1 0 0 c X e c b a X a a b b c c X b X e a X e c b a X a a b b c c X false c b a X b b c c X false c b a X b c c X false c b a X a b b c c X false NaTT certifiable-1.6